This invention relates to a combine harvester and particularly to a technique for improving crop throughput rate by reducing the quantity of straw passed through the combine.
A combine harvester generally includes a header which is mounted on a feeder housing, the header including a cutter knife across the front edge for cutting a standing crop. A transport system on the header transports the cut crop to the central feeder housing for transportation through the feeder housing into the combine body. The height of the cutter knife is adjusted relative to the crop by lifting the header vertically on the feeder housing.
The farmer operating the combine attempts to reduce the amount of crop material entering the combine by setting the height of the cutter knife higher on the crop stem to take the head and a reduced amount of the stem or straw. This of course leaves standing straw in the field behind the combine.
This standing straw must be accommodated in the next action on the field, whether that is a single pass tillage system or whether that is a first of several passes of a conventional tilling system. However this next tilling action can become difficult or impractical where the standing straw is of a length generally greater than the spacing between the shanks on the seeding of cultivating system.
These opposing requirements therefore generally obligate the farmer to cut the crop at a longer length of straw fed into the combine than would otherwise be desirable. This of course reduces the combine efficiency and increases combining costs.
An alternative process which has been proposed is that of a carrying out a second action to cut the straw after the combining process is complete. Some farmers carry out this process using a swather in a second cutting simply to cut straw. A chopper specially mounted on the swather can be used to spread the straw or alternatively the swather canvas can be removed to allow the cut straw to fall directly to the ground. This is of course highly inefficient in that it requires an additional pass over the field.
Another technique uses a separate mower to cut the standing straw in a separate action after the combine. For this purpose it has been proposed to use the conventional sickle knife cutting system which can be moved relatively quickly across the field. Alternatively some farmers utilize a rotary mower or a flail mowing system to cut the standing straw. This however involves an additional process involving additional costs and further movement across the field.
At the present time, therefore, the equipment available is generally unsatisfactory.
A proposal has apparently been made for a combine harvesting system used both in Australia and Europe which includes a stripper header. This header, instead of cutting the straw, strips the head of the crop from the straw and uses the combine to operate only upon the heads which have been stripped. Normally this leaves the whole length of the straw standing in the field. In one publication, the details of which are not available, it was proposed to add an additional cutting knife to the combine. However no details of the arrangement were disclosed in the publication. The combine then includes a cutting knife which cuts down the remaining straw.
It is one object of the present invention, therefore, to provide an improved combine harvester which allows the operator to cut the length of the crop carried into the combine body to be selected to provide improved combine operating efficiency.